Piezoelectric based resonant mass sensor using phase measurement

The paper presents design, development and testing of a resonant sensor to measure mass in the range of 0-12 g. The sensor is built using cantilever structure with piezoelectric excitation, sensing and microcontroller based closed loop electronics. The sensor measures the unknown mass by measuring the shift in resonance frequency of the cantilever beam. The shift in resonance frequency for a change in mass is detected by measuring the phase difference between the piezoelectric sensor output and actuator input using microcontroller. The proposed measurement system is simple and accuracy is found to be ±1.2% of full scale deflection.     

Resonance based DC current sensor

The paper presents design, development and testing of a resonant proximity DC current sensor to measure current in the range of 0-20 mA. The sensor is built using cantilever structure with piezoelectric excitation, sensing and closed loop electronics. The sensor measures the DC current by measuring the shift in resonance frequency of the cantilever beam. The proposed measurement system is novel, simple and accuracy is found to be 1.1% of full scale deflection.     

Thin film thickness measurements in two phase annular flows using ultrasonic pulse echo techniques

The electric power generation and oil/gas production industries have a strong interest in the physical characterization of conducting and non-conducting liquid films that are formed during the flow of liquids in pipes. Conducting and non-conducting liquid films do not lend themselves to the same characterization techniques due to the different requirements originating from their electrical properties. Techniques based on the use of ultrasound are extremely attractive for that purpose as they do not depend on the electrical properties of the liquid and are also non-invasive. This paper presents the application of ultrasonic techniques for measuring the thickness of wavy thin liquid films (<6 mm) in vertical pipes. Initial benchtop experiments were performed, and different signal processing methods were implemented in order to identify the most suitable depending on the film thickness. For a film thickness >0.5 mm a time of flight method was utilized whereas for a film thicknesses <0.5 mm a frequency method and time domain method were utilized. These methods were validated using a theoretical volume measurement on a static system. The studied methods were then tested on downward and upward vertical flow experimental rigs with pipe diameters of 127 mm and 34.5 mm respectively. The results of the experiments using ultrasonic methods showed good agreement with the measurements obtained using a multi pin film sensor and a concentric conductance probe, highlighting the potential that ultrasound offers in thin film measurements.     

压电复合悬臂梁非线性模型及求解

基于功能材料的复合悬臂梁涉及多物理场耦合,其本构关系的非线性影响悬臂梁的输出及控制精度,采用Helmholtz Gibbs自由能关系建立压电材料的非线性本构模型。基于Boltzmann原理,该模型的内核函数由热能和Gibbs能量平衡决定。将模型与悬臂梁结构进行耦合,利用边界和初始条件导出压电复合悬臂梁的强解形式,并对强解进行弱化,采用Galerkin法对弱解进行离散化,利用三次B样条函数得到悬臂梁的数值解。研究结果表明,与已有文献的实验进行比较,所建立的压电材料非线性本构模型能够较好地预测复合悬臂梁的行为。     

含多个压电元件智能悬臂梁的横向振动特性

本文以含多个压电元件的悬臂梁为例,基于Bernoulli-Euler梁的阶梯折算法,结合压电智能悬臂梁段的等效弹性模量理论,计算了多个压电元件的悬臂梁的固有频率和振型,并与有限元和等截面梁的计算结果进行比较。计算分析表明,压电材料尺寸和位置变化对智能悬臂梁结构的横向振动特性具有显著的影响,分析结论对高速飞行器结构设计和主动振动控制中压电元件的优化布置有实用价值。     

PZN-PT based smart probe for high temperature fluid viscosity measurements

A smart sensing system is proposed for high-temperature (up to 90 °C) viscosity measurement of viscous fluids. The proposed sensing system is based on a smart cantilever probe on which a new generation of piezoelectric materials, relaxor ferroelectric Pb(Zn(1/3)Nb(2/3))O(3−x)PbTiO(3) (PZN-PT), is bonded. The proposed system utilizes a PZN-PT single crystal for actuation and a laser displacement sensor for vibration detection. By analyzing the vibrational properties of the cantilever probe, the viscosity of measured fluids at different temperatures (up to 90 °C) were extracted. Lab tests were carried out to verify and evaluate the effect of this system on high-temperature measurements. Results show a consistent agreement with theoretical analysis. In comparison to the existing high-performance piezoelectric material, lead magnesium niobate-lead titanate solid solution (1−x)[Pb(Mg1/3Nb2/3)O3]−x[PbTiO3] (PMN-PT), PZN-PT has a steady performance at high temperatures and shows more reliability. The proposed sensing system can be applied to real-time monitoring of viscous fluids in high-temperature environments, such as vehicle cooling systems, power plant cooling tower fluid monitoring, and other heat transfer systems.     

Fabrication and characterization of PMN-PT single crystal cantilever array for cochlear-like acoustic sensor

We have successfully fabricated piezoelectric PMN-PT single crystal cantilever array. Each PMN-PT cantilever has a different length to achieve different resonance frequencies. The width and thickness of PMN-PT cantilever array are 200 μm and 10 μm, respectively. Resonance frequencies of PMN-PT cantilevers were measured with laser interferometer, and charge sensitivity was measured with charge-measuring device. PMN-PT cantilever array was installed in a noise-shield case. The array was then exposed to sound pressure frequency corresponding to resonance frequency to measure its sensitivity. The experimental results show that the PMN-PT cantilever array has high sensitivity to the sound pressure. This implies that the single crystal PMN-PT cantilever array is a potential candidate for a cochlear-like acoustic sensor.     

Differential resistance feedback control of a self-sensing shape memory alloy actuated system

There is a growing trend towards miniaturization, and with it comes an increasing need for miniature sensors and actuators for control. Moreover situations occur wherein implementation of external physical sensor is impossible, here self-sensing lends its hand appropriately. Though self-sensing actuation (SSA) is extensively studied in piezoelectric, exploring this property in shape memory alloy is still under study. A simple scheme is developed which allows differential resistance measurement of antagonistic shape memory alloy actuated wires to concurrently sense and actuate in a closed loop system. The usefulness of the proposed scheme is experimentally verified by designing a one link manipulator arm and is performed in a real time tracking control. In a practical implementation of the self-sensing actuator a newly proposed signal processing electronic circuit is used for direct differential resistance feedback control upto a bandwidth of 1.8 Hz. The control design uses fuzzy PID which requires no detailed information about the constitutive model of SMA. At an operating frequency of 1 Hz, the result of the self-sensing feedback control with an angular tracking accuracy of ±0.06° over a movement range of ±15° is demonstrated.     

压电分流阻尼控制悬臂梁振动的实验研究

采用压电分流阻尼原理,对根部粘贴压电陶瓷片的柔性悬臂梁振动控制进行了实验研究。实验中设计了一个由电容、电阻和运算放大器组成的等效电感电路,解决了压电分流电路设计中的超大电感器问题。根据测试得到的带压电分流电路悬臂梁的闭路和开路自然频率,确定出了压电分流电路的最优参数,对悬臂梁的瞬态振动和单频简谐激励下的稳态振动控制实验表明了压电分流阻尼被动控制结构振动的有效性。     

Simple liquid pumping system using piezoelectric actuated cantilever beam

A simple liquid pumping system is designed using a piezoelectric actuated cantilever beam with a glass tube attached to its tip. The flowrate of the pump is proportional to the tip displacement and vibrating frequency of the cantilever beam. The flowrate linearly increases up to 0.53 mL/s for water with actuation voltage (with amplitudes up to 300 V_(p-p)) applied to the piezoelectric actuator. The effect of other important parameters such as viscosity of the liquid, level of the liquid in the vessel and tube diameter on the flowrate of the pump is experimentally evaluated. The results demonstrate that the proposed pump is applicable to liquids with viscosity ranging from 0.23 to 170 mPa s.     

自供电无线传感网络节点设计

针对无线节点续航难题,提出一种自供电无线传感网络节点设计方案。该方案采用双晶悬臂梁式压电振子自发电结构,针对传统以电容为存储介质的能量收集电路的缺陷,采用新型压电能量收集存储芯片LTC3588-1及LTC4071搭建电路,设计无线节点模块并进行试验分析。试验结果表明:该方案能量收集效率高,可满足占空比为1%的无线传感网络节点工作需求,且适应于各种复杂振动环境。     

悬臂梁振动自适应模糊控制及DSP实现

以粘贴压电自感作动器的悬臂梁为研究对象,推导了悬臂梁振动主动控制的压电元传感方程和作动方程的传递函数,给出了压电自感作动器位置配置优化方法,设计了硬件电路以及软件流程.试验结果表明,利用压电自感作动器和模糊自适应控制器可有效地抑制悬臂梁振动.     

压电智能悬臂梁的压电片位置、尺寸及控制融合优化设计

对压电智能悬臂梁振动控制中的压电片的位置、尺寸及其控制参数进行研究.在对压电片和基板的耦合特性进行分析的基础上,建立智能悬臂梁的压电传感、致动方程及基于闭环控制系统的状态方程,并以系统的存留能量作为目标函数,建立压电智能悬臂梁压电片的位置、尺寸和控制参数的优化模型及一阶灵敏度分析表达式,并采用移动渐进线法(Method of moving asymptotes,MMA)对模型进行求解.采用Simulink对优化结果的动态响应特性进行仿真分析,仿真结果表明,采用提出的优化模型及算法对悬臂梁压电片的位置、尺寸和控制参数进行优化是合理的.     

压电分流阻尼控制悬臂梁振动的参数优化分析

采用阻抗分析技术,根据压电材料的机电耦合特性和RLC电路的电学阻抗特性,详细推导了RLC串联压电分流阻尼系统的机械阻抗特性,研究了作单模态振动的悬臂梁在粘贴压电片后形成的压电悬臂梁系统的位移传递函数特性。借助于调谐质量阻尼减振理论,进行了压电分流阻尼系统的参数优化分析,并通过算例验证了参数优化前后压电分流阻尼系统对悬臂梁振动的被动控制效果。     

压电智能悬臂梁结构振动主动控制仿真

为了提高LQR最优控制方法对压电类智能结构的振动控制效果,推导了表面离散分布压电元件的柔性悬臂梁结构的驱动和传感方程以及梁的弯曲振动方程,用模态分析方法对方程进行解耦和模型降阶,建立控制系统的状态空间方程。利用有限元分析方法来衡量压电元件对梁固有特性的影响,对状态空间方程的自振频率和振型函数进行修正,得到更为精确的数学模型。通过一悬臂梁的LQR最优控制仿真实例表明,经过模型修正后的最优振动控制效果更好。     

压电悬臂梁采收低频振动能的理论分析与仿真

采收环境振动能量为无线网络传感器供电是近年来研究的热点,目前还没有一个完整的理论和解决方案.文中设计了一种压电悬臂梁结构的环境振动能量采收装置,研究了悬臂梁压电振子结构受激励后产生电荷量与频率的关系,并进行了ANSYS仿真,得出了最佳的机电耦合模型和压电悬臂梁几何尺寸对固有频率的影响的关系.为采收环境低频振动能量,实现网络传感器自供电装置提供了设计的理论依据.     

On the Mathematical Modeling of a MEMS-Based Sensor for Simultaneous Measurement of Fluids Viscosity and Density

This paper discusses a novel microelectromechanical sensor for simultaneous measurement of fluids viscosity and density. Its operation is based on a longitudinal piezoelectric actuation of a micro-beam in a laminar fluid field. The proposed sensor consists of a micro-beam and a micro-cylindrical sensing element immersed in a fluid. In order to actuate the sensor longitudinally, the micro-beam is bonded with two piezoelectric layers on its upper and lower surfaces which are subjected to an AC voltage. The coupled governing partial differential equations of the micro-beam and fluid field have been derived. The obtained governing differential equations with time-varying boundary conditions have been transformed to an enhanced form with homogeneous boundary conditions. The enhanced equations have been discretized over the beam and fluid domain using Galerkin based reduced order model. The dynamic response of the sensing element for different piezoelectric actuation voltages and different exciting frequencies has been investigated. The effects of viscosity and density of fluids and geometrical parameters of the sensor on sensing element response have been studied.     

基于槽式悬臂梁结构的微质量传感器设计

压电式微质量传感器的测试精度直接依赖于结构频率对质量变化的灵敏程度。本文利用对称槽型梁和压电薄膜组成的对称敏感结构,提出了一种提高传感器灵敏度的结构设计方法,并设计了一种高精度谐振式微质量传感器。建立了结构频率变化对吸附质量敏感性的分析模型,并研究了槽型截面参数、自振频率及振动模态对灵敏度的影响。与矩形截面结构进行了仿真与实验对比,结果表明,相同几何尺寸参数下,槽型截面悬臂梁的一阶自振频率为1 851 Hz,矩形截面悬臂梁的一阶自振频率为1 610 Hz,相应的传感器灵敏度则分别为3.12×10⁴ Hz/g和1.5×10⁴ Hz/g,前者是后者的2倍。该项设计为提高微质量传感器灵敏度提供了一种新思路。     

悬臂梁双压电晶片振子发电性能研究

以双压电晶片振子为研究对象,对悬臂梁式双压电晶片振子在正压电效应下电压输出特性进行了有限元分析与试验研究,给出了压电晶片在悬臂梁上的最佳粘贴位置,并且利用有限元分析软件建立了悬臂梁双压电晶片振子的有限元模型,进行了结构尺寸参数对悬臂梁双压电晶片振子输出电压影响规律的仿真分析;利用压电陶瓷发电能力测试系统进行了试验测试,通过仿真和试验结果对比分析,得出了结构尺寸参数对悬臂梁双压电晶片振子发电的输出电压影响规律。     

基于构型优化的高阶模态微质量传感器灵敏度提升方法

高灵敏度是微质量传感器准确探测细菌、病毒和气体等物质的关键指标。虽然借助微型化的高阶模态梁振动可以有效提升探测灵敏度,但微尺度效应也降低了传感器的抗环境干扰能力。因此,如何在特定尺度约束下提升高阶模态传感器的灵敏度已成为谐振式微传感器设计的前沿问题。本文在研究弹性梁几何构型、压电层尺寸与有效质量分布对振动模态影响关系的基础上,建立了压电驱动多阶梯梁式微质量传感器的灵敏度分析模型,以传感器灵敏度提升最大为目标,建立了高阶振动模态下悬臂梁几何构型优化设计模型,得到了在不同振动模态下具有最高灵敏度的悬臂梁构型,使同尺寸传感器的灵敏度提升了10.0~15.0倍。考虑驱动位置与制造成本约束,设计并研制了具有六阶梯梁结构的高阶模态微质量传感器。实验结果表明,总长度为17.6mm的六阶梯梁微质量传感器的灵敏度为18.8×10~4 Hz/g,考虑制造误差的影响,其二阶模态灵敏度为同尺寸等截面梁传感器的10.0倍,较一阶模态同尺寸传感器灵敏度提升了19.8倍,从而验证了所提出的高阶模态微质量传感器灵敏度提升方法的有效性和可行性。